Diabetic retinopathy is a complication of diabetes that induces visual impairment, and is a leading cause of blindness. According to the U.S. Centers for Disease Control and Prevention, 45% of patients diagnosed with diabetes develop diabetic retinopathy. Altered retinal blood flow is an early consequence of the disease, and may contribute to vascular damage that occurs as the disease progresses. Thus, understanding the pathogenesis of vascular dysfunction is essential to preventing later stages of diabetic retinopathy. From its onset, diabetic retinopathy is characterized by an inability of the retinal blood supply to match neuronal demand for uninterrupted delivery of oxygen and nutrients. In the retina, most of these interactions take place at the level of capillaries, where pericytes, the only contractile cells at this level, adjust capillary diameter in response to neuronal signals. Th neurotransmitter acetylcholine, released by cholinergic neurons, induces pericyte-mediated vasodilation. Both pericytes and cholinergic neurons are structurally compromised in diabetic retinopathy. It is unclear, however, whether this translates into impaired vasomotor function. To address this, in Aim 1 we will test the hypothesis that decline in vasomotor ability of pericytes and changes in their gap junction coupling mediate impaired vasomotor control in diabetic retina. We will (1a) measure pericyte activity in response to electrical and chemical stimulation, then (1b) determine whether decreased gap junction coupling reduces pericyte activity propagation. This is relevant, since individual pericytes control local capillary diameter, while signaling between pericytes via gap junctions allows for the spatial distribution of vasomotor control. In Aim 2, we will test the hypothesis that reduced vascular sensitivity to cholinergic signaling and a decline in cholinergic amacrine cell function both impair vasomotor activity. First we will (2a) use cholinergic agonists and antagonists to determine whether the efficacy of cholinergic regulation of capillary diameter is compromised in diabetic retina. Then, (2b) we will use an optogenetic approach to directly activate cholinergic amacrine cells, to determine whether they are functionally compromised. Altered retinal blood flow is a common characteristic of patients with early stages of diabetic retinopathy, and likely contributes to latr complications of the disease. Functional compromises to the cells responsible for regulating blood flow in the retina may account for this vasomotor deficit. Understanding the mechanisms of vasomotor dysfunction could reveal novel therapeutic targets, and provide additional approaches for treating diabetic retinopathy.